Flow equalization reactor having multiple wastewater treatment zones

ABSTRACT

A method of treating wastewater is disclosed in which a flow equalization reactor is provided that includes at least one wastewater treatment zone. A first wastewater treatment process is performed in the at least one wastewater treatment zone, which can be switched to a second wastewater treatment process. The flow equalization reactor is designed with a variable liquid depth and volume that can operated as a mixed wastewater zone, an anaerobic reactor zone, an anoxic reactor zone or an aerobic reactor zone. The equalization reactor provides sufficient variable liquid depth and volume above a minimum liquid depth and residual volume to provide the necessary hydraulic flow equalization or surge volume to achieve a relatively constant effluent pumping rate or feed forward flow rate over 24 hours per day, seven days per week into the downstream biological treatment processes, clarifiers, filters, or disinfection units, etc.

FIELD OF THE DISCLOSURE

A wastewater treatment system including a flow equalization reactor isdisclosed, in which at least one wastewater treatment zone is providedwithin the variable liquid depth and volume flow equalization reactor.The flow equalization reactor provides sufficient variable liquid depthand volume above a minimum liquid depth and residual volume to providethe necessary hydraulic flow equalization or surge volume to achieve arelatively constant effluent pumping rate or feed forward flow rate over24 hours per day, seven days per week into the downstream biologicaltreatment processes, clarifiers, filters, or disinfection units, etc.

BACKGROUND

In a typical wastewater treatment facility, a population of bacteria isgrown and maintained to biologically remove organic pollutants, such asnitrogen or phosphorous, and to reduce the biochemical oxygen demand(BOD) of the wastewater. The bacteria are maintained in reactors holdingthe wastewater to be treated. Depending on the nature of the bacteriaand the desired biological removal that these bacteria perform, thereactors are operated under, for example, aerobic, anoxic, or anaerobicconditions.

Different reactors operating under different conditions may be combinedto provide a sequential treatment with successive removal of pollutants.For example, it is possible to combine in series an anaerobic reactor,an anoxic reactor, and an aerobic reactor followed by a final clarifier.Additionally, aerobic mixed liquor can be recycled to the anoxic reactorand return activated sludge can be recycled to the anaerobic reactor.

Further, it is known from U.S. Pat. No. 9,005,442 to equalize awastewater inflow into a flow equalization reactor to minimize thevariations of the wastewater inflow rate into the wastewater treatmentfacility. Nonetheless, it is desirable to further improve theeffectiveness of the treatment process under varying conditions, such aschanges in composition of the wastewater and/or of the wastewater inflowrate.

SUMMARY OF THE DISCLOSURE

Disclosed herein is a method of treating wastewater in a flowequalization reactor (EQ reactor) with variable liquid depth and volumethat can be designed and operated with or without internal partitions tosegregate the EQ reactor into a plurality of wastewater treatment zones.

In particular, a method of treating wastewater is disclosed whichincludes providing a flow equalization reactor having at least onewastewater treatment zone; receiving an inflow of wastewater into theflow equalization reactor; performing a first wastewater treatmentprocess in the at least one wastewater treatment zone; conducting anoutflow from the at least one wastewater treatment zone to a downstreamwastewater treatment stage; and, switching from the first wastewatertreatment process to a second wastewater treatment process in the atleast one wastewater treatment zone; wherein at least one of the firstwastewater treatment process and the second wastewater treatment processis a biological wastewater treatment process.

Moreover, a method of treating wastewater in a dual train or multi-trainwastewater treatment system is disclosed which includes providing atleast two flow equalization reactors upstream of a dual train ormulti-train wastewater treatment system; and, operating the at least twoflow equalization reactors in series.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will now be described with reference to the drawingswherein:

FIG. 1 shows a wastewater treatment system 100 including an equalizationreactor 110 that is operated as an anoxic denitrification reactor;

FIG. 2 shows a wastewater treatment system 200 including an equalizationreactor 210 that is divided into two wastewater treatment zones bypartition wall 220;

FIG. 3 shows a wastewater treatment system 300 in which an anoxic mixedliquor recycle flow is conducted from the anoxic denitrificationtreatment zone 310B to the anaerobic biological phosphorous treatmentzone 310A;

FIG. 4 shows a wastewater treatment system 400 in which equalizationreactor 410 is divided into three wastewater treatment zones by twopartition walls 220;

FIG. 5 shows a wastewater treatment system 500 in which about 55% of theoutflow from anoxic denitrification treatment zone 510B is pumped toconstant volume nitritation reactor 510C and about 45% of the outflowfrom anoxic denitrification treatment zone 510B is pumped to mixing cell520;

FIG. 6 shows a wastewater treatment system 600 including an equalizationreactor 610A operated as an anoxic denitrification treatment reactorfollowed by a downstream constant liquid level and volume nitritationreactor 610B;

FIG. 7 shows a dual train wastewater treatment system 700 containingequalization reactor 710 provided upstream of anammox reactors 300A and300B;

FIG. 8 shows a dual train wastewater treatment system 800 including twoflow equalization reactors 810 and 810′, which are each divided into twowastewater treatment zones;

FIG. 9 shows a dual train wastewater treatment system 900 in which anoutflow from wastewater treatment zones 910B1 and 910B2 is mixed with abypass flow from wastewater treatment zones 910A1 and 910A2 in mixingcell 920;

FIG. 10 shows a dual train wastewater system 1000 in which equalizationreactor 1010 is divided into two separate process trains 1010A1 and1010A2;

FIG. 11 shows partition wall 220 containing flow holes 1110 providednear the wall bottom; and,

FIG. 12 shows dividing curtain 1200, which also contains flow holestowards the bottom.

DESCRIPTION OF THE BEST AND VARIOUS EMBODIMENTS

The foregoing and other objects, aspects, and advantages of thedisclosure will be better understood from the following detaileddescription of the best and various embodiments. Throughout the variousviews and illustrative embodiments of the present disclosure, likereference numbers are used to designate like elements.

In a typical embodiment, the biological wastewater treatment process isselected from the group consisting of carbonaceous biological oxygendemand (BOD) removal, luxury biological phosphorous uptake, nitriteremoval, nitrate removal, nitrite and nitrate removal, and ammoniumnitrogen removal.

In another typical embodiment, the first wastewater treatment processand the second wastewater treatment process are biological wastewatertreatment processes.

In yet another typical embodiment, the first wastewater treatmentprocess or the second wastewater treatment process is not a biologicalwastewater treatment process and is selected from the group consistingof a variable volume wastewater storage, wastewater mixing, andaeration, or a combination thereof.

In a particular embodiment, the inflow Q of wastewater is screened rawwastewater, screened stormwater, a mixture of screened raw wastewaterand screened stormwater, a primary clarifier effluent, a dissolved airflotation (DAF) pretreatment system effluent, an anaerobic lagooneffluent, or an anaerobic reactor effluent.

In another particular embodiment, the outflow from the at least onewastewater treatment zone has a substantially constant pumping rate orfeed forward flow rate.

In yet another particular embodiment, at least one partition wall orcurtain is provided in the flow equalization reactor to define two ormore wastewater treatment zones, wherein the at least one partition wallor curtain has an opening at or near the bottom so that the two or morewastewater zones in the flow equalization reactor operate at asubstantially similar variable liquid level.

Typically, the downstream wastewater treatment stage is selected fromthe group consisting of a downstream nitrification stage, a downstreamnitritation stage, an anammox reactor stage, and a final clarifierstage.

Also typically, a nitrate or nitrite mixed liquor recycle flow line isprovided for recycling a partially treated effluent from a downstreamwastewater treatment stage to an upstream wastewater treatment stage.Moreover, a nitrate or nitrite mixed liquor recycle flow through therecycle line is typically of from 100% to 400% of the inflow Q into theflow equalization reactor.

With particularity, a return activated sludge line is provided forrecycling activated sludge from a downstream wastewater treatment stageto an upstream wastewater treatment stage. Also with particularity, areturn activated sludge flow through the return activated sludge line isof from 50% to 200% of the inflow of wastewater into the flowequalization reactor.

In a typical embodiment, an anoxic mixed liquor recycle flow of from 50%to 200% of the inflow Q is provided from a downstream wastewatertreatment zone to an upstream wastewater treatment zone. In anothertypical embodiment, the method further includes providing a nitritemixed liquor recycle flow from a nitritation reactor into the firstwastewater treatment zone of the flow equalization reactor; obtaining atotal outflow out of the flow equalization reactor, the total outflowhaving a volume corresponding to a total volume of the inflow Q and thenitrite recycle flow; conducting about 55% of the total inflow from theflow equalization reactor into a nitritation reactor as a flow Q1;receiving about 45% of the total inflow from the flow equalizationreactor as a flow Q2; and, mixing the flow Q1 and the flow Q2.

In another typical embodiment, the method further includes receiving themixture of the flow Q1 and the flow Q2 in an anammox reactor. In yetanother typical embodiment, an outflow from the anammox reactor isreceived in a final clarifier.

In a particular embodiment, the method further includes providing afirst return activated sludge flow from the final clarifier into thenitritation reactor; and, providing a second return activated sludgeflow from the final clarifier into the anammox reactor. In anotherparticular embodiment, the first return activated sludge flow is of from0% to 20% of the inflow of wastewater into the flow equalizationreactor, and the second return activated sludge flow is of from 80% to200% of the inflow of wastewater into the flow equalization reactor.Both return activated sludge flows can exist continuously at the sametime or can be independently cycled on and off.

With particularity, the method further includes operating a first flowequalization reactor as a first stage anaerobic reactor as part of anenhanced biological phosphorous removal process; conducting an outflowfrom the first flow equalization reactor to a second flow equalizationreactor; operating the second flow equalization reactor as an anoxicdenitrification reactor for biological nitrite and nitrate nitrogenremoval; and, operating a third flow equalization reactor as an aerobicnitrification reactor for biological ammonia nitrogen removal.

Turning to the drawings, FIG. 1 shows a wastewater treatment system 100including an equalization reactor 110 that is operated without anypartitions, thereby allowing the entire inner space of the reactor 110to be used for equalizing the wastewater inflow Q as well as forperforming a first biological treatment process. In this case, theequalization reactor is operated as an anoxic denitrification reactor inwhich denitrifying bacteria convert some of the nitrate to nitrogen gasunder very low concentrations of, or in the absence of, dissolved oxygen(DO). Pump 140 pumps an effluent from the EQ reactor to a constantvolume nitrification reactor 120 for converting ammonium nitrogen intonitrite nitrogen and nitrate nitrogen. Nitrate recycle (NR) line 172 isprovided to return nitrate produced in the nitrification reactor to theEQ reactor. Typically, the nitrate recycle flow is of from 200% to 400%of the total daily inflow Q into the wastewater treatment system. Fromthe nitrification reactor 120, treated effluent is conducted to finalclarifier 130 through line 160. Sludge is allowed to settle in the finalclarifier 130 while treated water is discharged to the receiving streamvia line 170.

Activated sludge is returned from the final clarifier through returnactivated sludge (RAS) line 174, which may be returned to thenitrification reactor 120 via line 176 and/or to the EQ reactor via line178. Valve 150 is provided to turn on and off or to adjust the RAS flow.

FIG. 2 shows a wastewater treatment system 200 including an equalizationreactor 210 that is divided into two wastewater treatment zones bypartition wall 220. The inflow Q is first received in wastewatertreatment zone 210A where anoxic denitrification takes place. Throughflow holes 1110 provided at or near the bottom of the partition wall,partially treated wastewater flows into the second treatment zone 210B,which is operated as either an anoxic denitrification section or as anaerobic nitrification section. Equalization reactor 210 equalizes theinflow into the downstream treatment stages by receiving a varyinginflow Q and providing a substantially constant outflow, which is pumpedinto the downstream nitrification reactor. Moreover, the liquid levelwithin the first and the second wastewater treatment zones 210A and 210Bis substantially the same, even though the total liquid level within theEQ reactor varies with varying inflow Q.

FIG. 3 shows a wastewater treatment system 300 in which an equalizationreactor 310 is divided into treatment zones 310A and 310B. An anoxicrecycle (AR) flow is conducted from the anoxic denitrification treatmentzone 310B through line 320 to the anaerobic biological phosphorousremoval treatment zone 310A. An effluent from treatment zone 310B ispumped to a nitrification reactor. Subsequently, the effluent from thenitrification reactor is conducted to a final clarifier. Further, a RASline recycles activated sludge from the final clarifier to one or moreof the treatment zone 310A, treatment zone 310B, and the nitrificationreactor.

FIG. 4 shows a wastewater treatment system 400 in which two partitionwalls 220 divide equalization reactor 410 into three wastewatertreatment zones. Inflow Q flows into the first treatment zone 410A,which is operated as an anaerobic biological phosphorous treatment zone.Partially treated wastewater flows into the second wastewater treatmentzone 410B, which is operated as an anoxic denitrification treatmentzone. Subsequently, wastewater flows into the third treatment zone 410C,which is operated as an aerobic nitrification zone.

The liquid levels within each of the three wastewater treatment zones410A through 410C are substantially similar, even though the totalliquid level varies in all three treatment zones with varying inflow Q.

FIG. 5 shows a wastewater treatment system 500 in which a partition wall220 separates the first treatment zone 510A from the second treatmentzone 510B. The liquid levels in zones 510A and 510B are substantiallysimilar. The partition of the third treatment zone 510C, however, doesnot include flow holes. Thus, the third reactor zone is operated as aconstant volume reactor. In particular, zone 510C is operated as anitritation reactor.

The nitrite recycle line 540 returns a nitrite mixed liquor recycle flow(NITR) from nitritation reactor 510C to the first wastewater treatmentzone 510A, which is operated as an anaerobic biological phosphoroustreatment zone, and/or to the second wastewater treatment zone 510B,which is operated as an anoxic denitrification treatment zone. Thenitrite mixed liquor recycle flow is from 200% to 400% of the inflow Q.Thus, the total outflow out of the reactor zone 510B is the sum of theinflow Q and the nitrite recycle flow NITR.

The total outflow out of the second treatment zone 510B is bifurcated,and about 55% of the outflow from anoxic denitrification treatment zone510B, i.e., Q₁, is pumped to the constant volume nitritation reactor510C and about 45% of the outflow from anoxic denitrification treatmentzone 510B, i.e., Q₂, is pumped to mixing tank 520. Accordingly, the flowQ₁ is 0.55·(Q+NITR) and Q₂ is 0.45 (Q+NITR).

The combined liquors from the mixing cell flow into the constant volumereactor 530, which is operated as an anammox reactor. Specifically,anammox reactor 530 contains bacteria mediating the direct conversion ofnitrite and ammonium into nitrogen gas by the anaerobic ammoniumoxidation (anammox) process that is used for deammonification ofwastewater without the intermediate production of nitrate. The dissolvedoxygen (DO) concentrations in the anammox reactor is kept between 0 mg/Land 0.2 mg/L.

From the reactor 530 an effluent is conducted to a final clarifier.Further, activated sludge may be recycled to nitritation reactor 510Cwith a flow of 0% to 20% Q and/or to the anammox reactor 530 with a flowof 80% to 200% Q.

FIG. 6 shows a wastewater treatment system 600 including an equalizationreactor 610A operated as an anoxic denitrification treatment zone andconstant volume nitritation reactor 610B. Nitrite recycle line 620returns an NITR flow to the anoxic denitrification treatment zone 610A.An outflow Q₁ of 0.55·(Q+NITR) is pumped into the constant volumenitritation reactor 610B and an outflow Q₂ with 0.45 (Q+NITR) is pumpedinto a mixing cell. The combined and mixed effluents from the mixingcell flow into an anammox reactor. After deammonification in the anammoxreactor, the effluent is conducted into a final clarifier.

FIG. 7 shows a dual train wastewater treatment system 700 containingequalization reactor 710 provided upstream of anammox reactors 300A and300B. In a typical municipal wastewater treatment system, the biologicaltreatment process has at least two process trains to provide systemredundancy and reliability. In the depicted dual train system 700, twoEQ reactors are provided within the basin of EQ reactor 710. Flow holesare provided in the partition walls or curtains between treatment zones710A1 and 710B1 on the one hand, and between treatment zones 710A2 and710B2 on the other hand. However, the partition wall between zones 710A1and 710A2 and between zones 710B1 and 710B2 does not have flow holes.Similarly, wastewater can flow through flow holes from zones 710B1 and710B2 into zones 710C1 and 710C2, respectively, but no flow is providedbetween zones 710C1 and 710C2.

FIG. 8 shows a dual train wastewater treatment system 800 including twoflow equalization reactors 810 and 810′, which are each divided into twowastewater treatment zones. Specifically, EQ reactor 810 is divided intotreatment zones 810A1 and 810B1 and EQ reactor 810′ is divided intotreatment zones 810A2 and 810B2.

FIG. 9 shows a dual train wastewater treatment system 900 wherein anoutflow from wastewater treatment zones 910B1 and 910B2 is mixed with abypass flow from wastewater treatment zones 910A1 and 910A2 in mixingcell 920.

FIG. 10 shows a dual train wastewater system 1000 in which anequalization reactor basin is divided into two separate process trains1010A1 and 1010A2. Thus, two EQ reactors are provided in a dual trainsystem at the head of the dual train. In the depicted embodiment, a fivestage biological nutrient removal process is provided, wherein the EQreactor basin is designed to run EQ reactor treatment zone 1010A1 as afirst stage anaerobic bio-P equalization reactor in series with EQreactor treatment zone 1010A2 operated as a second stage anoxicdenitrification reactor. Both treatment zones 1010A1 and 1010A2 provideflow equalization. Thereby the dual train system 1000 provides a fivestage rather than a four stage biological treatment system to achieveboth luxury P removal and biological nitrogen removal.

In particular, in the embodiment of FIG. 10 an inflow of wastewater Q isreceived in treatment zone 1010A1 to undergo anaerobic bio-P removal.Subsequently, partially treated wastewater flows into the secondtreatment zone 1010A2, which is an anoxic denitrification treatmentzone. Accordingly, the first treatment zones of the two process trainsare connected in series. Further, an anoxic recycle flow 1010 isprovided from the anoxic denitrification treatment zone 1010A2 to theanaerobic bio-P removal treatment zone 1010A1 with a total flow of 1Q to2Q.

From the second treatment zone 1010A2, an outflow is pumped into thethird stage wastewater treatment reactors 1010B1 and 1010B2. The flowrate is measured with flow meter 1020. The third stage wastewatertreatment reactors 1010B1 and 1010B2 are operated as constant volumenitrification reactors. A nitrate recycle flow is provided fromtreatment reactors 1010B1 and 1010B2 to the anoxic denitrificationtreatment zone 1010A2 with a flow of 2Q to 4Q.

Additionally, wastewater flows from each of the third wastewatertreatment reactors 1010B1 and 1010B2 into the fourth stage wastewatertreatment reactors 1010C1 and 1010C2, respectively. Thus, downstream ofthe equalization reactors 1010A1 and 1010A2 the treatment proceeds inparallel within the two process trains.

An overflow from the fourth wastewater treatment reactors 1010C1 and1010C2 is discharged to the fifth stage reactors 1010D1 and 1010D2,respectively, which are operated for aerobic treatment. Subsequently, anoverflow from the fifth stage reactors 1010D1 and 1010D2 is dischargedinto a flow splitter 1011 and then is conducted to final clarifiers. Areturn activated sludge line recycles activated sludge from the finalclarifiers to the anoxic denitrification treatment zone 1010A2.

FIG. 11 shows a partition wall 220 having flow holes 1110 provided nearthe wall bottom, which allow wastewater to flow from its currenttreatment zone into the next treatment zone by gravity flow whileproviding the requisite retention time for wastewater in its currentzone. In addition, FIG. 11 shows the low level mark LL and the highlevel mark HL showing the minimum level and the maximum level of thewastewater, respectively, in an EQ reactor.

FIG. 12 shows a dividing curtain 1200, which also contains flow holestowards the bottom and which may be used as an alternative to apartition wall.

In all of the above-described exemplary embodiments, at least onewastewater treatment zone of the EQ reactor basin is used as abiological reactor. Thus, the EQ reactor may be a single basin with nosections or zones or a single basin with multiple biological reactorsections. The treatment zones or sections of the EQ reactor basin thatare designed and used as biological reactors maintain a variable mixedliquor suspended solids concentration and biomass weight as required toachieve continuous biological luxury uptake for phosphorus removal; or,biological denitrification for nitrite and/or nitrate removal; or,carbonaceous BOD removal; or, biological nitrification for ammonianitrogen removal.

In addition, the EQ Reactor basin may also include a zone or sectionthat is not a biological reactor but that contains variable volumestorage and mixing; or storage, mixing and aeration of screened rawwastewater, primary clarifier effluent wastewater, pretreated DAF celleffluent, or anaerobic lagoon or reactor effluent wastewater. Such awastewater equalization section or zone of the EQ reactor basinfunctions to provide variable volume hydraulic flow equalization only,and does not provide biological treatment by an anaerobic, anoxic oraerobic reactor process. Equalized wastewater flow is pumped out of orflows out by gravity from this wastewater equalization section or zone.Multiple pipes, pumps, and/or multiple rate of flow controllers areprovided to conduct the effluent to multiple and different downstreamtreatment processes.

If the EQ reactor treatment zones provide capability for receivingrecycle flow such as RAS recycle flow or anoxic recycle flow ornitrite/nitrate mixed liquor recycle flow; and, use process equipmentthat provides the capability for operation with independent aeration andmixing; or, mixing without aeration, then the EQ reactor zones can beindependently controlled to function with great process flexibility.This flexibility includes, but is not limited to aerated or unaeratedwastewater equalization; carbonaceous BOD removal; luxury biologicalphosphorus removal; nitrite and/or nitrate removal, and ammonia removal.Moreover, this flexibility allows the EQ reactor to be optionallyoperated, for example, in an emergency as a constant depth, maximumvolume, or, variable depth, variable volume aerobic reactor for BOD andammonia nitrogen removal if the downstream constant volume nitrificationreactor must be taken out of service. Additional flexibility isprovided, if process equipment with independent mixing and aerationcapability is used to operate the sections or zones of the EQ reactor inan aerated, aerobic condition at high or higher liquid levels andvolumes, and, in an unaerated, anoxic condition at low or lower liquidlevels and volumes. For example, if the EQ Reactor is divided into twosections, the first section may be operated as an anoxic denitrificationreactor and the second section as an aerobic nitrification reactor whenthe EQ Reactor is at high or higher liquid levels; while both sectionsof the EQ Reactor may be operated as an anoxic denitrification reactorat low or lower liquid levels.

Thus, in a typical embodiment, a first biological treatment process isperformed in a particular treatment zone and then the process isswitched over to a second biological treatment process when desired ornecessitated by changes in treatment zone mixed liquor suspended solidsconcentration and/or biomass weight, wastewater composition,temperature, or flow rate of inflow Q without losing the ability toequalize the wastewater inflow Q. At a later time, the second biologicaltreatment process may be switched back to the first process or toanother treatment process.

However, it is also possible to switch between a biological wastewatertreatment process and a non-biological wastewater treatment process,such as variable volume wastewater storage, wastewater mixing, oraeration, in one of the treatment zones of an EQ reactor.

Typical combinations of the EQ reactor design are provided in Table 1below:

TABLE 1 Waste- Anoxic Aerobic Downstream Downstream water EQ AnaerobicDenite Nitrification Nitrification Nitritation Comb. Zone BioP Zone ZoneZone Reactor Reactor #1 X X #2 X X X #3 X X X #4 X X X X #5 X X X #6 X X

In combination #1, an anoxic denitrification treatment zone in an EQreactor is followed by a downstream nitrification reactor. Incombination #2, an aerobic nitrification treatment zone is additionallyprovided within the EQ reactor.

In combination #3, the EQ reactor includes an anaerobic biologicalphosphorous removal zone and an anoxic denitrification zone.Additionally, a downstream nitrification reactor is provided.Combination #4 has, additionally, an aerobic nitrification zone withinthe EQ reactor.

Combination #6 includes an anoxic denitrification EQ reactor zonefollowed by a downstream constant volume nitritation reactor withgravity nitrite recycle flow back into the anoxic EQ reactor zone.Combination #5 additionally includes a wastewater equalization zoneupstream of the biological treatment zones.

The EQ reactor design and operation is therefore very flexible dependingupon the downstream biological reactor process required and the totalvariable hydraulic flow equalization volume required. All the reactorsections or zones of the EQ reactor have approximately equal variableliquid depth ranging between the low liquid level minimum residualvolume and the high liquid level maximum storage volume. The partitionwall(s) 220 or curtains 1200 in the EQ reactor segregate the basin intoseparate process zones that operate at substantially similar variableliquid depth between low and high liquid levels. The partition wallstherefore have only openings in the partition at or near the bottom ofthe basin to allow wastewater to flow by gravity head from the first, tothe second, to the third sections as required. The locations of thepartition walls or curtains in the EQ reactor basin are selected ordesigned to provide the desired or required treatment process volume ineach section between the low liquid level and the high liquid level.

In a typical municipal wastewater treatment system, the biologicaltreatment process has at least two process trains in order to providesystem redundancy and reliability. By providing an EQ reactor for eachprocess train, great flexibility is achieved in the treatment system.Thus, in a particular embodiment, at least two EQ reactors are providedwith a dual train or multi-train wastewater treatment system. If two EQreactors are provided in a dual train system upstream of an existingdual train, four stage biological nitrogen removal system, then the EQreactor can be designed to optionally run in series with EQ reactor #1operated as first stage anaerobic bio-P equalization reactor #1 and withEQ reactor #2 operated as second stage anoxic denitrification reactor#2. Thereby, the dual train is used to provide five stage rather than afour stage biological treatment system to achieve both luxury P removaland biological nitrogen removal.

The embodiments described hereinabove are further intended to explainbest modes known of practicing it and to enable others skilled in theart to utilize the disclosure in such, or other, embodiments and withthe various modifications required by the particular applications oruses. Accordingly, the description is not intended to limit it to theform disclosed herein. Also, it is intended that the appended claims beconstrued to include alternative embodiments.

The foregoing description of the disclosure illustrates and describesthe present disclosure. Additionally, the disclosure shows and describesonly the preferred embodiments but, as mentioned above, it is to beunderstood that the disclosure is capable of use in various othercombinations, modifications, and environments and is capable of changesor modifications within the scope of the concept as expressed herein,commensurate with the above teachings and/or the skill or knowledge ofthe relevant art.

The term “comprising” (and its grammatical variations) as used herein isused in the inclusive sense of “having” or “including” and not in theexclusive sense of “consisting only of.” The terms “a” and “the” as usedherein are understood to encompass the plural as well as the singular.

All publications, patents and patent applications cited in thisspecification are herein incorporated by reference, and for any and allpurpose, as if each individual publication, patent or patent applicationwere specifically and individually indicated to be incorporated byreference. In the case of inconsistencies, the present disclosure willprevail.

What is claimed is:
 1. A method of treating wastewater comprising:providing a flow equalization reactor having at least one wastewatertreatment zone; receiving an inflow of wastewater into the flowequalization reactor; performing a first wastewater treatment process inthe at least one wastewater treatment zone; conducting an outflow fromthe at least one wastewater treatment zone to a downstream wastewatertreatment stage; and, switching from the first wastewater treatmentprocess to a second wastewater treatment process in the at least onewastewater treatment zone; wherein at least one of the first wastewatertreatment process and the second wastewater treatment process is abiological wastewater treatment process.
 2. The method according toclaim 1, wherein the biological wastewater treatment process is selectedfrom the group consisting of carbonaceous biological oxygen demand (BOD)removal, luxury biological phosphorous uptake, nitrite removal, nitrateremoval, nitrite and nitrate removal, and ammonium nitrogen removal. 3.The method according to claim 1, wherein the first wastewater treatmentprocess and the second wastewater treatment process are biologicalwastewater treatment processes.
 4. The method according to claim 1,wherein the first wastewater treatment process or the second wastewatertreatment process is not a biological wastewater treatment process andis selected from the group consisting of a variable volume wastewaterstorage, wastewater mixing, and aeration, or a combination thereof. 5.The method according to claim 1, wherein the inflow Q of wastewater isscreened raw wastewater, screened stormwater, a mixture of screened rawwastewater and screened stormwater, a primary clarifier effluent, adissolved air flotation (DAF) pretreatment system effluent, an anaerobiclagoon effluent, or an anaerobic reactor effluent.
 6. The methodaccording to claim 1, wherein the outflow from the at least onewastewater treatment zone has a substantially constant pumping rate orfeed forward flow rate.
 7. The method according to claim 1, furthercomprising: providing at least one partition wall or curtain in the flowequalization reactor to define two or more wastewater treatment zones,wherein the at least one partition wall or curtain has an opening at ornear the bottom so that the two or more wastewater zones in the flowequalization reactor operate at a substantially similar variable liquidlevel.
 8. The process according to claim 1, wherein the downstreamwastewater treatment stage is selected from the group consisting of adownstream nitrification stage, a downstream nitritation stage, ananammox reactor stage, and a final clarifier stage.
 9. The methodaccording to claim 1, further comprising: providing a nitrate and/ornitrite mixed liquor recycle flow (NIR) line from a downstreamwastewater treatment stage to an upstream wastewater treatment stage.10. The method according to claim 9, wherein a nitrite and/or nitratemixed liquor recycle flow through the NIR line is of from 100% to 400%of the inflow Q into the flow equalization reactor.
 11. The methodaccording to claim 1, further comprising: providing a return activatedsludge line from a downstream wastewater treatment stage to an upstreamwastewater treatment stage.
 12. The method according to claim 11,wherein a return activated sludge flow through the return activatedsludge line is of from 50% to 200% of the inflow of wastewater into theflow equalization reactor.
 13. The method according to claim 7, furthercomprising: providing an anoxic mixed liquor recycle flow of from 50% to200% of the inflow Q from a downstream wastewater treatment zone to anupstream wastewater treatment zone.
 14. The method according to claim 1,further comprising: providing a nitrite mixed liquor recycle flow from anitritation reactor into the first wastewater treatment zone of the flowequalization reactor; obtaining a total outflow out of the flowequalization reactor, the total outflow having a volume corresponding toa total volume of the inflow Q and the nitrite mixed liquor recycleflow; conducting about 55% of the total inflow from the flowequalization reactor into a nitritation reactor as a flow Q₁; receivingabout 45% of the total inflow from the flow equalization reactor as aflow Q₂; and, mixing the flow Q₁ and the flow Q₂.
 15. The methodaccording to claim 14, further comprising: receiving the mixture of theflow Q₁ and the flow Q₂ in an anammox reactor.
 16. The method accordingto claim 15, further comprising: receiving an outflow from the anammoxreactor in a final clarifier.
 17. The method according to claim 16,further comprising: providing a first return activated sludge flow fromthe final clarifier in the nitritation reactor; and, providing a secondreturn activated sludge flow the final clarifier to the anammox reactor.18. The method according to claim 17, wherein the first activated sludgeflow is of from 0% to 20% of the inflow of wastewater into the flowequalization reactor, and wherein the second activated sludge flow is offrom 80% to 200% of the inflow of wastewater into the flow equalizationreactor.
 19. A method of treating wastewater in a dual train ormulti-train wastewater treatment system comprising: providing at leasttwo flow equalization reactors upstream of a dual train or multi-trainwastewater treatment system; and, operating the at least two flowequalization reactors in series.
 20. The method according to claim 19,further comprising: operating a first flow equalization zone or reactoras a first stage anaerobic reactor for biological phosphorous removal;conducting an outflow from the first flow equalization zone or reactorto a second flow equalization zone or reactor; operating the second flowequalization zone or reactor as an anoxic denitrification reactor forbiological nitrogen removal; and, operating a third flow equalizationzone or reactor as an aerobic nitrification reactor for biologicalammonia nitrogen removal.